This invention relates generally to gas turbine engine, and more particularly, to methods for replacing combustor liner panels used with gas turbine engines.
A turbine engine includes a compressor for compressing air which is mixed with a fuel and channeled to a combustor wherein the mixture is ignited within a combustion chamber for generating hot combustion gases. At least some known combustors include a dome assembly, a cowl assembly, and liners to channel the combustion gases to a turbine, which extracts energy from the combustion gases for powering the compressor, as well as producing useful work to propel an aircraft in flight or to power a load, such as an electrical generator. The liners are coupled to the dome assembly with the cowl assembly, and extend downstream from the cowl assembly to define the combustion chamber.
At least some known cowl assemblies are two piece assemblies that include an inner and an outer cowl. Because the inner and outer cowls are coupled to the liners, each cowl may be subjected to mechanical stresses and vibratory stresses induced from the combustor. In addition, either cowl may be subjected to different stresses than the other respective cowl. Over time, continued exposure to such stresses may cause one, or both, cowls to deteriorate, and limit the useful life thereof.
To facilitate reducing the effects of stresses that may be induced to the cowl assemblies, at least some known two-piece cowl assemblies include a wire-wrapped portion wherein each cowl is formed with a lip at the leading edge thereof. More specifically, the cowl lip is formed by curling or wrapping the cowl around a damper wire. However, during operation a thermal mismatch may occur between the cowl body and the wire. Over time, continued operation with the thermal mismatch may cause the cowl to unwrap from around the wire such that a gap is created between the wire and the cowl. When vibratory loading is induced to the cowls, the gap may permit the cowl to shake against the wire, which over time may result in damage and deterioration of the two-piece cowl assembly. Current repair methods for two-piece cowl assemblies include removing the deteriorated inner and/or outer cowl and replacing the deteriorated cowl with replacement cowl that includes the wire-wrapped portion. However, because the cowl assembly is coupled to the liner and the dome assembly, often the entire combustor must be disassembled for either cowl to be replaced. Furthermore, when the fasteners are removed from the cowl assembly and dome assembly, precise dimensional relations between the components may be altered and as a result, special tooling may be required during reassembly. Thus, replacing a wire-wrapped cowl may be a time-consuming and expensive process.
In one aspect, a method for replacing a portion of a gas turbine engine combustor is provided. The combustor includes a combustor liner and a wire-wrapped cowl assembly that includes an inner cowl and an outer cowl. The method comprises cutting through the wire-wrapped cowl assembly upstream from fastener openings used to couple the inner and outer cowls to the combustor liner, removing a portion of the cowl assembly from the combustor, and coupling a replacement cowl to the portion of the existing cowl assembly that is downstream from the cut, wherein the replacement cowl includes an inner annular portion, an outer annular portion, and a plurality of circumferentially-spaced radial ligaments extending therebetween.
In another aspect, a method for replacing a portion of a deteriorated cowl assembly within a gas turbine engine combustor is provided. The deteriorated cowl assembly includes an inner surface, an outer surface, and a wire-wrapped portion. The method comprises cutting substantially radially through the deteriorated cowl assembly between the outer and inner surfaces of the deteriorated cowl assembly, removing the wire-wrapped portion of the deteriorated cowl assembly that is upstream from the cut extended through the cowl assembly, and coupling a replacement cowl onto the combustor to replace the portion of the deteriorated cowl assembly removed from the combustor, wherein the replacement cowl includes an inner annular portion and an outer annular portion that is substantially concentric with respect to the annular inner portion.